Abstract:

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We have formed high density nanodots of nickel silicide (NiSi) on ultrathin SiO2 and
characterized their electronic charged states by using an AFM/Kelvin probe technique. Si
quantum dots (Si-QDs) with an areal dot density of ~2.5x1011cm-2 were self-assembled on
~3.6nm-thick thermally-grown SiO2 by controlling the early stages of LPCVD using pure SiH4
gas. Subsequently, electron beam evaporation of Ni was carried out as thin as ~1.7nm in
equivalent thickness at room temperature and followed by 300°C anneal for 5min in vacuum.
XPS and AFM measurements confirm the formation of NiSi dots with an average dot height of
~8nm. After removal of Ni residue on SiO2 by a dilute HCl solution, bias conditions required
for electron charging to NiSi dots were compared with those to pure Si-QDs dots and Ni dots.
The surface potential changes stepwise with respect to the tip bias due to multistep electron
injection and extraction of NiSi nanodots. In addition, it is confirmed that charge retention
characteristics of NiSi dots are superior to those of Si-QDs with the almost same size.

Abstract: This paper presents positron lifetime results which give information on the nature of
vacancy defects induced by electron irradiation in bulk nitrogen doped (nD-nA= 2.3x1017 cm-3) Cree 6H-SiC. The electron irradiations have been performed at different energies and with different fluences from 5􀂗1017 e-cm-2 to 3􀂗1018 e-cm-2. Positron lifetime have been measured with a 22NaCl source as a function of temperature between 15 and 300 K. The lifetime spectra were analyzed as sums of two exponential lifetime components 􀁗i weighted by the intensities Ii, convoluted with the resolution function. From the temperature dependence of the lifetime spectra
we can infer that several vacancy defects exist in the electron irradiated n-type 6H-SiC. The nature of detected vacancy defects depends on the electron energy.

Abstract: The degradation and recovery behavior of device performance on GaAlAs LEDs (Light
emitting diodes) irradiated by 2-MeV electrons and 70-MeV protons are investigated. The reverse
current increases after irradiation, while the capacitance decreases. The device performance
degradation is proportional with fluence. For electron irradiation, fluence rate is also effective for
degradation. Low fluence rate shows more large degradation compared to high fluence rate
resulting from heat impact in bulk. DLTS measurement reveals the DX center in epitaxial substrate,
and this spectrum increases with fluence. The radiation damage of proton is larger than that of
electron irradiation, which is caused by the difference of mass and possibility of nuclear collision
for the formation of lattice defects. After irradiation, the device performance recovers by thermal
annealing.

Abstract: This paper deals with imaging by means of backscattered electrons in the high resolution
scanning electron microscopy. Possible backscattered electrons detection systems are outlined and
one of the most efficient, the high take of angle single crystal scintillation detector, is described in
detail. Its advantages and disadvantages are discussed and the comparison with the secondary
electron detection modes is shown. The high resolution micrographs taken by the backscattered
electron detector as well as by the secondary electron detectors are displayed.

Abstract: Theoretical calculation indicates that the large exponential-doping GaAs photocathodes have a much narrower electron energy distribution than traditional GaAs NEA cathodes, and the excellent performance attributes to the special structure characters of the band-bending region and lower negative electron affinity of the new-type GaAs photocathodes. The effects of surface doping concentration and work function on the energy distribution are discussed in details, and the FWHM of the energy distribution is less than 100meV. The simulation results indicate that the large exponential-doping mode further improves the features of the electron energy spreads for GaAs photocathodes, which may meet the further demand of next generation of electron guns.

Abstract: The equipment for measuring electron beam (EB) focus in electron beam produced by the effect of extremum temperature of powder molten pool caused by the interactive effect of electron beam with metal powder is described. The principle of operation of apparatus and examples of EB characteristics are presented. During electron beam processing, the mechanical analysis of metal powder molten pool temperature following focusing current are studied. As a result, the transferring point of critical energy density described by the peak of metal powder pool temperature can be obtained. Based on the temperature characteristics of critical energy density, the measuring concept of dynamic focal spot of electron beam is put forward in the paper. The method of measuring dynamic focal spot of electron beam will provide a new possibility for 3D scanning prototyping through changing focus position of EB.